A network topology is the pattern of links between nodes where a given node has one or more links to other nodes in the network. Physical topologies of networks include spanning tree, ring, mesh and bus, and among them a ring network is one in which the nodes are connected in a closed loop configuration and in which data is passing in sequence from node to node between adjacent nodes. A logical topology is the nature of the paths that signals follow from node to node, and in many instances the logical and physical topologies are similar. In the logical ring topology, the data flows in a closed loop clockwise or counterclockwise.
Fiber optic rings are often deployed as part of both metropolitan area networks (MANs) and wide area networks (WANs). A resilient packet ring (RPR) is a wired network topology deployed for fiber optic rings and designed for using RPR access protocol and physical layer interfaces to produce high-speed data transmission. A network with RPR topology has dual counter rotating rings (clockwise, counterclockwise) where multiple nodes can transmit on both rings simultaneously.
For increased bandwidth, load balancing and availability of communication channels between nodes (e.g., switches and stations), link aggregation or trunking, according to IEEE standard 802.3ad, is a method of grouping physical network links into a single logical link. With link aggregation, it is possible to increase capacity of communication channels between nodes using their Fast Ethernet and Gigabit Ethernet technology. Two or more Gigabit Ethernet connections can be grouped to increase bandwidth, and to create resilient and redundant links. Standard local area network (LAN) technology provides data rates of 10 Mbps, 100 Mbps and 1000 Mbps and, for obtaining higher capacity (e.g., 10000 Mbps) link aggregation allows grouping of 10 links; and where factors of ten (10) are excessive, link aggregation can provide intermediate rates by grouping links with different rates.
Wired network protocols are designed to meet RPR standards (IEEE 802.17) and aim to improve scalability and bandwidth allocation and throughput of fiber optic rings in order to meet the demands of packet-switched networks. A typical RPR supports SONET/SDH (155 Mbps to 10 Gbps) standards as well as Ethernet PHY (Ethernet physical layer interface which meets 1 Gbps to 10 Gbps rates). An RPR network carries control messages on opposite rings from data, and in the event of fiber or node failure it is required by the RPR standards (IEEE 802.17) to satisfy 50 milliseconds recovery time.
Rapid spanning tree protocol (RSTP, standard IEEE 802.1D-2004), for instance, relies on active spanning tree topology and is one in which a network can rapidly reconfigure its topology in case of a failure. With the RSTP the spanning tree re-assigns ports and learns their new MAC addresses.